1. Field of the Invention
This invention relates in general to the detection and analysis of reflections of a regular translational source of electro-magnetic wave radiation from preselected, unidentified., target surfaces. More particularly, the present invention relates to a method for the remote identification of a preselected, unidentified, homogeneous target surface.
2. Description of the Prior Art
It is known in the literature that the Stokes parameters of light emerging from the top of the earth's atmosphere may be predicted as a function of sun angle and viewing angle when viewing extensive areas of the earth over which the reflecting and polarizing properties are reasonably uniform. These predictions depend on detailed measurements of reflecting and polarizing properties of various materials, such as sand, clay and grass, when illuminated by sunlight. See Final Report "Experiment SO46:Visible Radiation Polarization Measurements:Phase C," NASA DOC. NAS9-7267, page 1, January, 1968. See also Oetken, "Polarimetric Methods in Astrophysics" JENA REVIEW, Vol. 15, page 330, June, 1970, which describes that to obtain the physical conditions of objects, the radiation from these objects is converted to Stokes parameters from which the degree of polarization (intensity), polarization directions, etc. is determined.
Moreover, there is described in an article by Cacciani and Fofi, "A Complete Stokes-Meter," Solar Physics, Vol. 19, pp. 270-276 (1971), apparatus for measuring Stokes parameters resulting from incident and reflected radiation. Also taught by Cacciani and Fofi is that the state of partially polarized radiation may be determined by the use of (1) azimuth determination, (2) its intensity and (3) the non-polarized background.
However, heretofore, remote sensings of target surfaces have been conducted with polarimetry on a limited basis in specialized applications. General applications to ground truth, with remote sensings of reflected light, have faltered on three technical impediments: (1) there was no imaging polarimeter in being; (2) no simple procedure existed for evaluation of the intrinsic polarization intensity of a target surface as distinguished from the optical thickness between a light source and target surface as well as from a target surface through recording; and (3) there was no discrete index to gauge the correlation of data because of the stochastic character of optical waves in thin film phenomena. Consequently, in view of the fact that polarization is a stress sensitive parameter of light, interfacial dynamics under natural conditions have tended to mask polarization signatures of target surfaces. This masking effect and the stochastic characteristics of optical waves have impeded the development of imaging polarimetry.